The two main clinical dysfunctions of the prostate are benign prostatic hypertrophy and malignant disease. A number of innovative approaches to treat these diseases have been introduced over the last decade to try and replace the TURP and intraoperative surgical approaches. These include pharmacological manipulation through alpha-blockers, balloon dilatation, laser thermal ablation, focused ultrasound and transrectal or transurethral hyperthermia for BPH, and cryosurgical ablation under ultrasound guidance for carcinoma of the prostate. Photodynamic Therapy is a relatively new form of treatment for cancer and other hyper- proliferating tissues that uses a photoactivating drug and light to selectively destroy the targeted tissue. it has been recently shown by Selman that the prostate of older dogs selectively takes up and retains the second generation photosensitizer SnET2 relative to the urethra and bladder. Such selective uptake raises the possibility of generating selective photochemical coagulation of the central portion of the prostate while not producing serious negative physiological consequences. Preliminary studies in the dog have shown this to be possible. It is the objective of this project to expand the pilot study of the concept. This is to include the development of a transurethral balloon based diffused delivery system that can be used in the dog. The delivery system includes a dosimetry monitors at the urethra/balloon interface for accurate in- vivo dosimetry. Also interstitial illumination using cylindrical diffusers will be studied. The systems will be tested in dogs to determine their in-vivo performance along with determination of the optical characteristics of the prostate and to further evaluate the potential for generating selective necrosis of the gland. PROPOSED COMMERCIAL APPLICATION: If it is found that PDT could effectively treat BPH, or prostate cancer, the commercial potential for the technology being developed under this project would be significant. For BPH such a treatment could be done on an outpatient or office bases compared to the present TURP requiring hospitalization. At present there are 360,000 TURP procedures done annually in the USA for BPH at an average cost of $8,606 and 40,000 radical prostatectomies for cancer and BPH at an average cost of $12,788. It is estimated that PDT transurethral procedure could be performed at a cost of $2,800.